U.S. patent application number 12/376960 was filed with the patent office on 2010-07-01 for core network device, radio communication base station device, and radio communication method.
This patent application is currently assigned to Panasonic Corporation. Invention is credited to Takahisa Aoyama, Akito Fukui, Takeshi Kanazawa.
Application Number | 20100165905 12/376960 |
Document ID | / |
Family ID | 39106873 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100165905 |
Kind Code |
A1 |
Kanazawa; Takeshi ; et
al. |
July 1, 2010 |
CORE NETWORK DEVICE, RADIO COMMUNICATION BASE STATION DEVICE, AND
RADIO COMMUNICATION METHOD
Abstract
It is possible to provide a core network device, a radio
communication base station device, and a radio communication method
which can improve the radio resource use efficiency of the entire
network without increasing UE battery consumption. According to the
devices and the method, a user quantity counting unit (163) of UPE
(160) counts the number of UE which have performed a position
registration in each position registration area containing a
plurality of cells. A user quantity comparing unit (164) selects
MCT if the counted UE quantity is not smaller than a predetermined
threshold value and SCT if the counted UE quantity is smaller than
the predetermined threshold value, thereby appropriately performing
switching between SCT and MCT in accordance with the UE quantity.
Only when the SCT is selected by the UPE (160), eNB counts the
number of users in the cell managed by the local device.
Inventors: |
Kanazawa; Takeshi;
(Kanagawa, JP) ; Fukui; Akito; (Kanagawa, JP)
; Aoyama; Takahisa; (Kanagawa, JP) |
Correspondence
Address: |
Dickinson Wright PLLC;James E. Ledbetter, Esq.
International Square, 1875 Eye Street, N.W., Suite 1200
Washington
DC
20006
US
|
Assignee: |
Panasonic Corporation
Osaka
JP
|
Family ID: |
39106873 |
Appl. No.: |
12/376960 |
Filed: |
August 24, 2007 |
PCT Filed: |
August 24, 2007 |
PCT NO: |
PCT/JP2007/066446 |
371 Date: |
February 9, 2009 |
Current U.S.
Class: |
370/312 |
Current CPC
Class: |
H04W 72/005
20130101 |
Class at
Publication: |
370/312 |
International
Class: |
H04H 20/71 20080101
H04H020/71 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2006 |
JP |
2006-229811 |
Oct 5, 2006 |
JP |
2006-274080 |
Nov 16, 2006 |
JP |
2006-310271 |
Claims
1. A core network apparatus comprising: a user number counting
section that counts a number of users joining a multimedia
broadcast multicast service (MBMS) on a per tracking area basis; a
user number comparing section that compares the number of users
counted, with a predetermined threshold, so as to select, when the
number of users is equal to or greater than the threshold,
multi-cell transmission whereby a plurality of radio communication
base station apparatuses belonging to an identical frequency area
transfer multimedia broadcast multicast service data in
synchronization with each other, and select, when the number of
users is less than the threshold, single cell transmission whereby
a single radio communication base station apparatus accommodating
users joining the multimedia broadcast multicast service in a cell,
transfers multimedia broadcast multicast service data; and a
reporting section that reports one of multi-cell transmission and
single cell transmission selected, to a radio communication base
station apparatus under control.
2. The core network apparatus according to claim 1, further
comprising a distribution check section that selects, when the user
number comparing section selects single cell transmission, a
transmission mode based on a situation of distribution of radio
communication base station apparatuses subject to single cell
transmission.
3. The core network apparatus according to claim 2, wherein the
distribution check section selects multi-cell transmission when a
ratio of the number of radio communication base station apparatuses
subject to single cell transmission to a total number of radio
communication base stations per tracking area is equal to or
greater than a predetermined threshold.
4. A radio communication base station apparatus comprising: an
acquisition section that acquires from a core network apparatus a
command for one of multi-cell transmission whereby a plurality of
radio communication base station apparatuses belonging to an
identical frequency area transfer multimedia broadcast multicast
service (MBMS) data in synchronization with each other and single
cell transmission whereby a single radio communication base station
apparatus accommodating users joining the multimedia broadcast
multicast service within a cell transfers the multimedia broadcast
multicast service data; a counting section that performs counting
about a cell under control of the radio communication base station
apparatus only when a single cell transmission command is acquired;
and a transfer section that transfers the multimedia broadcast
multicast service data in a cell where there are users according to
the counting result.
5. The radio communication base station apparatus according to
claim 4, wherein, upon acquiring a command for single cell
transmission, the counting section causes the radio communication
terminal apparatus inside a cell under control of the radio
communication base station apparatus to transition into an active
mode for only a control channel and counts the number of users, on
a per cell basis.
6. The radio communication base station apparatus according to
claim 4, further comprising: a detection section that acquires a
received quality measurement result in a nearby cell measured by a
radio communication terminal apparatus and detects a radio
communication terminal apparatus located in cell edges based on the
acquired received quality measurement result; and a multicast
processing section that requests, when detecting the radio
communication terminal apparatus located in the cell edge, a
neighboring cell forming the cell edge, to join multimedia
broadcast multicast service.
7. The radio communication base station apparatus according to
claim 4, further comprising: a recounting period selection section
that selects a recounting period, which is an interval until next
counting is performed; and a parameter selection section that
selects a response probability, which is a condition for the radio
communication terminal apparatus that requests multimedia broadcast
multicast service to send a response message, wherein: upon
acquiring a command for single cell transmission, the counting
section controls the recounting period selection section and the
parameter selection section, so as to extend a recounting period
and reduce a response probability when the number of users inside
the cell is equal to or greater than a predetermined threshold or
shorten the recounting period and increase the response probability
when the number of users inside the cell is less than the
predetermined threshold.
8. The radio communication base station apparatus according to
claim 4, further comprising a multicast processing section that
inquires of other radio communication base station apparatuses
located in the boundary between neighboring tracking areas about
the multimedia broadcast multicast service delivery situation and
requests the other radio communication base station apparatuses
that do not provide multimedia broadcast multicast service to join
multimedia broadcast multicast service.
9. The radio communication base station apparatus according to
claim 4, further comprising: a detection section that detects, upon
acquiring a negative acknowledgement for requesting a
retransmission of lost multimedia broadcast multicast service data
and a received quality measurement result in a neighboring cell
measured by the radio communication terminal apparatus, a radio
communication terminal apparatus located in cell edges based on the
acquired received quality measurement result; a counting section
that counts the number of users located in the cell edge detected
by the detection section for each neighboring cell; a multicast
processing section that requests, when the number of users counted
for each neighboring cell is equal to or greater than a
predetermined threshold, the neighboring cell to join multimedia
broadcast multicast service; and a retransmission section that
retransmits, when the number of users counted for each neighboring
cell is less than the predetermined threshold, the multimedia
broadcast multicast service data requested by the negative
acknowledgment.
10. The radio communication base station apparatus according to
claim 9, wherein the counting section counts the number of users
located in cell edges bordering on a specific neighboring cell.
11. A radio communication terminal apparatus comprising: a data
decision section that decides whether or not received multimedia
broadcast multicast service data is lost and creates, upon deciding
that the multimedia broadcast multicast service data is lost, a
negative acknowledgment message for requesting a retransmission of
the lost multimedia broadcast multicast service data; a received
power measurement section that measures received power in each
neighboring cell; and a transmission section that transmits the
negative acknowledgment message and received power measurement
result in each neighboring cell to a radio communication base
station apparatus.
12. The radio communication terminal apparatus according to claim
11, wherein the received power measurement section measures
received power in a specific neighboring cell.
13. A radio communication method comprising: counting, by a core
network apparatus, a number of users joining a multimedia broadcast
multicast service (MBMS) on a per tracking area basis; comparing,
by a core network apparatus, the number of users counted, with a
predetermined threshold, so as to select, when the number of users
is equal to or greater than the threshold, multi-cell transmission
whereby a plurality of radio communication base station apparatuses
belonging to an identical frequency area transfer multimedia
broadcast multicast service data in synchronization with each
other, and select, when the number of users is less than the
threshold, single cell transmission whereby a single radio
communication base station apparatus accommodating a user joining
the multimedia broadcast multicast service within a cell transfers
multimedia broadcast multicast service data; reporting, by a core
network apparatus, one of multi-cell transmission and single cell
transmission selected, to radio communication base station
apparatuses under control of the core network apparatus; acquiring,
by a radio communication base station apparatus, a command for one
of multi-cell transmission and single cell transmission, from the
core network apparatus, counting, by a radio communication base
station apparatus, about the cell under control of the radio
communication base station apparatus only when a single cell
transmission command is acquired; and transferring, by a radio
communication base station apparatus, multimedia broadcast
multicast service data in a cell where there are users according to
the counting result.
Description
TECHNICAL FIELD
[0001] The present invention relates to a core network apparatus,
radio communication base station apparatus and radio communication
method for providing a multimedia broadcast/multicast service
(MBMS).
BACKGROUND ART
[0002] UMTS (Universal Mobile Telecommunications System) is a
third-generation mobile communication system which has evolved from
GSM (Global System for Mobile Communications), which is the
European standard and aims at providing further improved mobile
communication services based on a GSM core network (CN) and a WCDMA
(Wideband Code Division Multiple Access) wireless access
technique.
[0003] UMTS provides MBMS. MEMS is a more developed service for not
only broadcasting multimedia data but also multicasting multimedia
to users who subscribe to applicable services. For example, MBMS
provides a news channel, music channel, movie channel or the
like.
[0004] Non-Patent Documents 1, 2 and 3 describe an architecture and
processing procedure relating to MEMS.
[0005] FIG. 1 shows a reference architecture that supports MBMS on
a 3GPP UMTS network. As shown in FIG. 1, UMTS is constructed of
terminal (User Equipment: UE) 10, UTRAN 20 and core network (Core
Network: CN) 30.
[0006] UTRAN 20 is comprised of one or more radio network
sub-systems (RNS), and an RNS is comprised of one radio network
controller (RNC) 23 and one or more Nodes B (base stations) 21
under control of appropriate RNC 23.
[0007] RNC 23 is responsible for allocation and management of radio
resources and plays a role as an access point with respect to CN
30.
[0008] Node B 21 receives information transferred from the physical
layer of UE 10 via the uplink, or on the contrary, transfers data
to UE 10 via the downlink. Node B 21 assumes a role of access point
of UTRAN for UE 10.
[0009] UTRAN 20 makes up and maintains a radio access bearer (RAB)
for a call between UE 10 and CN 30.
[0010] CN 30 requests end-to-end service quality (Quality of
Service: QoS) requirements from the RAB and the RAB supports the
QoS requirements set up by CN 30. Therefore, UTRAN 20 makes up and
maintains the RAB, and therefore meets the end-to-end QoS
requirements.
[0011] MBMS is provided via a packet switching service. When
providing a packet switching service, RNC 23 is connected to SGSN
(Serving GPRS Support Node) 35 and GGSN (Gateway GPRS Support Node)
37 of CN 30. SGSN 35 supports communication with RNC 23 and GGSN 37
manages connections with other packet switching networks such as
the Internet.
[0012] MBMS is a downward dedicated service that provides a
streaming or background service for a plurality of UEs 10 using a
common or dedicated downward channel.
[0013] MBMS is divided into a broadcast mode and a multicast mode.
In the MBMS broadcast mode, multimedia data can be easily
transferred to all users located in a broadcast area. On the other
hand, in the MBMS multicast mode, multimedia data can be easily
transferred to a specific user group located in a multicast area.
Here, the broadcast area is an area where a broadcast service is
available and the multicast area is an area where a multicast
service is available.
[0014] Users who try to receive an MBMS receive a service
announcement provided by the network. Here, the "service
announcement" refers to reporting a list of services to be provided
in the future and related information to UEs. Furthermore, users
receive service notification provided by the network. Here,
"service notification" refers to notifying the UEs of information
about the broadcast data to be transferred.
[0015] Furthermore, users who want to receive an MBMS in the
multicast mode must particularly join a multicast subscription
group. The "multicast subscription group" refers to a group of
users who have completed a subscription procedure.
[0016] A user who has joined the multicast subscription group can
participate in (join) a multicast group to receive a specific
multicast service, that is, a user group who receive a specific
multicast service. The "multicast group" refers to a group of users
who receive a specific multicast service. "Joining" refers to
joining a multicast group who gather to receive a specific
multicast service and is also called "MBMS multicast activation."
Therefore, the user can receive specific multicast data through
MBMS multicast activation (or joining).
[0017] RNC 23 transfers MBMS user data to UE 10 via Node B 21
through the user plane of the UTRAN protocol. In order to transfer
the MBMS user data, UTRAN 20 makes up and maintains a radio bearer
for a call between UE 10 and CN 30. The MBMS radio bearer is
transferred only through a downlink.
[0018] The MBMS radio bearer plays a role of transferring user data
of one specific MBMS transferred from CN 30 to UTRAN 20 only to
specific UEs.
[0019] Furthermore, in the case of multicast mode, UTRAN 20 needs
to confirm the presence of UEs in the entire service area to
deliver MBMS user data only to Node B 21 where users are located.
Therefore, UTRAN 20 counts the number of UEs. UTRAN 20 reports UE
10 that UTRAN 20 is currently counting when providing information
about MBMS using a MBMS common control channel or performing paging
to a specific MBMS group.
[0020] Upon receiving the information that counting is being
performed on the corresponding service from the service
notification on MBMS, UE 10 transfers an RRC connection request
message to UTRAN through an uplink common channel to report UTRAN
20 that UE 10 wants to receive the corresponding MBMS and thereby
sets up an RRC connection (connection between the RRC entity of UE
10 and RRC entity of UTRAN 20). Here, UE 10 reports to UTRAN 20
that UE 10 wants to receive the corresponding MBMS using an RRC
connection request message.
[0021] Therefore, UTRAN 20 recognizes UE 10 that has transferred
the RRC connection request message and thereby recognizes the
presence of the user who requests a specific MBMS within the cell
and sets up an MBMS radio bearer if at least one user exists.
[0022] By the way, the 3GPP is currently studying a next-generation
core network and radio access network, and as for an MBMS transfer
method, the 3GPP is also studying the following two transfer
methods as standard candidates along with this.
[0023] FIG. 2 shows a conceptual diagram of the two transfer
methods. The first one is called "single cell transmission (SCT)"
as shown on the right side of FIG. 2, which performs counting to
check the presence/absence of users and performs data transmission
only to cells where there are users. Furthermore, when quality
deteriorates in cell edges or the like, SCT performs retransmission
or changes the modulation scheme to thereby improve received
quality of users.
[0024] The second one is called "multi-cell transmission (MCT)" as
shown on the left side of FIG. 2, whereby a plurality of base
stations belonging to the same frequency area (Single Frequency
Network: SFN) perform data transmission in synchronization with
each other and improve received quality of users through inter-cell
diversity combination irrespective of the presence/absence of
users.
Non-Patent Document 1: 3GPP TS 23.246"3rd Generation Partnership
Project; Technical Specification Group Services and System Aspects,
Multimedia Broadcast/Multicast Service (MBMS), Architecture and
functional description", 2006-06 Non-Patent Document 2: 3GPP TS
25.346 "3rd Generation Partnership Project, Technical Specification
Group Radio Access Network, Introduction of the Multimedia
Broadcast Multicast Service (MBMS) in the Radio Access Network
(RAN), Stage 2", 2006-06
Non-Patent Document 3: 3GPP TS 25.331"3rd Generation Partnership
Project, Technical Specification Group Radio Access Network, Radio
Resource Control (RRC), Protocol Specification", 2006-06
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0025] However, the above de scribed method for providing MBMS
selects MCT or SCT depending on a service and has the following
problems.
[0026] In MCT, multimedia data is only transferred to the SFN area,
and therefore when the number of users located in the SFN area is
small, the amount of data delivered to the cell with no user
increases, which may decrease the utilization efficiency of radio
resources of the entire network.
[0027] Furthermore, in SCT, counting is performed to transfer data
only to a specific user group, but with this counting, the user
needs to establish an RRC connection with Node B and thereby
consumes the battery. For this reason, when there are many users in
a given area, users exist in most cells in the area and the amount
of battery consumption of UEs may increase by the amount
corresponding to unnecessary counting compared to MCT.
[0028] It is therefore an object of the present invention to
provide a core network apparatus, radio communication base station
apparatus and radio communication method for improving the
utilization efficiency of radio resources of an entire network
without increasing battery consumption of UEs.
Means for Solving the Problem
[0029] The core network apparatus of the present invention adopts a
configuration including a user number counting section that counts
the number of users joining a multimedia broadcast/multicast
service (MEMS) on a per tracking area basis, a user number
comparing section that compares the number of users counted, with a
predetermined threshold, so as to select, when the number of users
is equal to or greater than the threshold, multi-cell transmission
whereby a plurality of radio communication base station apparatuses
belonging to an identical frequency area transfer MBMS data in
synchronization with each other, and select, when the number of
users is less than the threshold, single cell transmission whereby
a single radio communication base station apparatus accommodating
users joining the MBMS within a cell transfers MBMS data, and a
reporting section that reports one of multi-cell transmission and
single cell transmission selected, to a radio communication base
station apparatus under control.
[0030] The radio communication base station apparatus of the
present invention adopts a configuration including an acquisition
section that acquires from a core network apparatus a command for
one of multi-cell transmission whereby a plurality of radio
communication base station apparatuses belonging to an identical
frequency area transfer multimedia broadcast/multicast service
(MBMS) data in synchronization with each other, and single cell
transmission whereby a single radio communication base station
apparatus including users joining the MBMS within a cell transfers
the MBMS data, a counting section that performs counting about a
cell under control of the radio communication base station
apparatus only when a single cell transmission command is acquired,
and a transfer section that transfers the MBMS data in a cell where
there are users according to the counting result.
[0031] The radio communication method of the present invention
includes a user number counting step of a core network apparatus
counting the number of users joining a multimedia
broadcast/multicast service (MBMS) on a per tracking area basis, a
user number comparing step of comparing the number of users
counted, with a predetermined threshold, so as to select, when the
number of users is equal to or greater than the threshold,
multi-cell transmission whereby a plurality of radio communication
base station apparatuses belonging to an identical frequency area
transfer MBMS data in synchronization with each other, and select,
when the number of users is less than the threshold, single cell
transmission whereby a single radio communication base station
apparatus accommodating a user joining the MBMS within a cell
transfers MBMS data, a reporting step of reporting one of
multi-cell transmission and single cell transmission selected, to
radio communication base station apparatuses under control of the
core network apparatus, an acquiring step of a radio communication
base station apparatus acquiring a command for one of multi-cell
transmission and single cell transmission from the core network
apparatus, a counting step of counting about the cell under control
of the radio communication base station apparatus only when a
single cell transmission command is acquired, and a transfer step
of transferring MBMS data in a cell where there are users according
to the counting result.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0032] According to the present invention, it is possible to
improve the utilization efficiency of radio resources of an entire
network without increasing battery consumption of UEs.
BRIEF DESCRIPTION OF DRAWINGS
[0033] FIG. 1 shows a reference architecture that supports MBMS on
a 3GPP UMTS network;
[0034] FIG. 2 conceptually shows multi-cell transmission and single
cell transmission;
[0035] FIG. 3 shows a network configuration according to Embodiment
1 of the present invention;
[0036] FIG. 4 is a block diagram showing a configuration of the MME
shown in FIG. 3;
[0037] FIG. 5 is a block diagram showing a configuration of the UPE
shown in FIG. 3;
[0038] FIG. 6 is a sequence diagram showing a procedure for joining
a multicast subscription group;
[0039] FIG. 7 is a sequence diagram showing a session start
procedure;
[0040] FIG. 8 is a sequence diagram showing a procedure for mode
switching from SCT to MCT;
[0041] FIG. 9 is a block diagram showing a configuration of an eNB
according to Embodiment 1 of the present invention;
[0042] FIG. 10 is a flowchart showing are counting procedure in an
eNB according to Embodiment 2 of the present invention;
[0043] FIG. 11 is a block diagram showing a configuration of the
eNB according to Embodiment 2 of the present invention;
[0044] FIG. 12 is a block diagram showing a configuration of a UPE
according to Embodiment 3 of the present invention;
[0045] FIG. 13 is a sequence diagram showing a session start
procedure according to Embodiment 3 of the present invention;
[0046] FIG. 14 is a sequence diagram showing an inquiry about the
MBMS delivery situation between eNBs according to Embodiment 4 of
the present invention;
[0047] FIG. 15 is a block diagram showing a configuration of a UE
according to Embodiments 5 and 6 of the present invention; and
[0048] FIG. 16 is a block diagram showing a configuration of an eNB
according to Embodiments 5 and 6 of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0049] Hereinafter, embodiments of the present invention will be
explained in detail with reference to the accompanying
drawings.
Embodiment 1
[0050] FIG. 3 shows a network configuration according to Embodiment
1 of the present invention. The network shown in FIG. 3 is
comprised of terminal (User Equipment: UE) 100, radio base station
apparatus (Evolved Node B: eNB) 120, mobility management apparatus
(Mobility Management Entity: MME) 140, user plane apparatus (User
Plane Entity: UPE) 160 and broadcast/multicast service center
(Broadcast Multicast Service Center: BM-SC) 180, and eNB 120, MME
140 and UPE 160 are connected via an IP network respectively.
[0051] eNB 120 is in charge of allocation and management of radio
resources, receives information transferred from the physical layer
of UE 100 via the uplink, and, meanwhile, transfers data to UE 100
via the downlink. eNB 120 assumes a role as an access point of the
radio access network for UE 100.
[0052] MME 140 manages the location of UE 100 on a per tracking
area basis (TA) and also performs signaling about the setting,
correction and release of RAB jointly with UE 100. MME 140 stores a
context assigned in a network connection procedure of UE 100 and
associated with MBMS of UE 100. A plurality of MMEs 140 exist in a
given MBMS area and MME to which users are connected differs from
one user to another.
[0053] UPE 160 plays a role as gateway with respect to an outside
network, transfers a downlink packet to an eNB to which UE 100 is
connected according to the setting of RAB and transfers an uplink
packet to an appropriate outside network according to the
destination address of a packet. Only one UPE 160 exists within a
given MBMS area for each MBMS and stores contexts associated with
MEMS.
[0054] BM-SC 180 is located between an MEMS content server and UPE
160 and transfers information about the session type, the start and
end of a service and MBMS data to UPE 160.
[0055] FIG. 4 is a block diagram showing a configuration of MME 140
shown in FIG. 3. Input section 141 in FIG. 4 reports signals
inputted from BM-SC 180, UPE 160 and eNB 120 to user information
management section 142.
[0056] User information management section 142 compares the MEMS
reception performance of UE 100 with the performance of UE 100
included in the MEMS registration response reported from BM-SC 180
and required for the corresponding service. When this comparison
result shows that the MBMS reception performance of UE 100 exceeds
the performance of UE 100 required for the service, the service and
an identifier for the tracking area to which UE 100 belongs are
reported to user number counting section 143. When the MBMS
reception performance of UE 100 falls below the performance of UE
100 required for the service, suspension of the processing is
reported to BM-SC 180 and UE 100.
[0057] User number counting section 143 counts the number of
joining users, per service, on a per tracking area basis and
updates the number of users according to the service and the
tracking area identifier reported from user information management
section 142. The updated number of users is outputted to output
section 144. In this way, MME 140 can count the number of users
using location registrations of UEs as substitutes.
[0058] Output section 144 includes the number of users outputted
from user number counting section 143 in an MBMS registration
update and sends out the MBMS registration update to UPE 160.
[0059] FIG. 5 is a block diagram showing a configuration of UPE 160
shown in FIG. 3. In FIG. 5, input section 161 reports parameter
section 162 and user number counting section 163 of the signals
inputted from BM-SC 180, MME 140 and eNB 120. Especially, input
section 161 reports the number of MBMS users on a per tracking area
basis for each service included in the MBMS registration update to
user number counting section 163.
[0060] Parameter section 162 manages various parameters related to
data paths and outputs the service data inputted from BM-SC 180
from output section 165 according to the parameter setup.
[0061] User number counting section 163 counts the number of
joining users, per service, on a per tracking area basis. Since a
plurality of MMEs 140 exist in the MEMS area, the number of users
under control of UPE 160 is a total value of the numbers of users
reported from the respective MMES. Therefore, UPE 160 can know the
number of users joining the service that exist in the MEMS area on
a per tracking area basis. User number counting section 163 having
received the MEMS registration update updates the number of users
joining the service and outputs the updated number of users to user
number comparing section 164.
[0062] User number comparing section 164 compares the number of
users outputted from user number counting section 163 with a
predetermined threshold for each tracking area. When the comparison
result shows that the number of users is equal to or greater than
the threshold, user number comparing section 164 selects MCT as a
transmission mode in the tracking area or selects SCT when the
number of users is less than the threshold. An identifier
indicating the selected MCT or SCT is outputted to output section
165.
[0063] Output section 165 as a reporting section outputs the
service data outputted from parameter section 162 and the
identifier indicating MCT or SCT outputted from user number
comparing section 164 to eNB 120.
[0064] Next, a procedure for a user to join a multicast
subscription group will be explained. FIG. 6 is a sequence diagram
showing a procedure for joining a multicast subscription group.
[0065] In step (hereinafter abbreviated as "ST") 201, UE 100 which
has received a service announcement sends out a multicast
subscription request to MME 140. This multicast subscription
request includes an identifier indicating a multicast group UE 100
wants to join.
[0066] In ST 202, MME 140 having received the multicast
subscription request performs a procedure for approval of the user
jointly with BM-SC 180. This approval procedure is conducted based
on the user's subscriber contract information and judges whether or
not the user can receive a service correctly.
[0067] When the approval procedure is completed successfully, MME
140 sends out a request for MBMS context activation to UE 100 in ST
203.
[0068] In ST 204, UE 100 having received the MBMS context
activation request sends out an MBMS context activation request to
MME 140. The MBMS context activation request includes performance
or the like to receive MBMS of UE 100 itself.
[0069] When UE 100 is the first to join the multicast group of the
service, MME 140 having received the MBMS context activation
request sends out an MBMS registration request to BM-SC 180 in ST
205. When UE 100 is not the first to join the multicast group of
the service, the processing in ST 205 and ST 206 will not be
performed. The MEMS registration request includes an identifier of
UPE 160 to deliver MBMS data.
[0070] In ST 206, BM-SC 180 having received the MEMS registration
request transmits an MBMS registration response including the
performance of UE 100 required for the service to MME 140.
[0071] In ST 207, MME 140 counts the number of joining users, per
service, on a per tracking area basis and updates the number of MME
users. In ST 208, MME 140 sends out the MBMS registration update to
UPE 160. The MBMS registration update includes the updated number
of MBMS users on a per tracking area basis.
[0072] In ST 209, UPE 160 counts the number of users joining the
service who exist within the MEMS area on a per tracking area basis
and updates the number of UPE users. In ST 210, MME 140 transmits
acceptance of MEMS context activation to the UE.
[0073] The processing described so far completes the procedure for
the user to join the multicast subscription group. The number of
MME users is also updated likewise when the user leaves the
multicast group or when the tracking area of UE 100 is updated and
the update result is reported to UPE 160 and UPE 160 also updates
the number of UPE users.
[0074] Next, the session start procedure will be explained using
FIG. 7. Upon detecting the start of a given MEMS service, BM-SC 180
sends out a session start request to UPE 160 in ST 301.
[0075] In ST 302, user number comparing section 164 of UPE 160
having received the session start request compares the number of
users joining the service who exist within the MEMS area with a
predetermined threshold for each tracking area. When the number of
joining users is equal to or greater than the threshold, MCT is
selected as the transmission mode in the tracking area and when the
number of joining users is less than the threshold, SCT is
selected.
[0076] When MCT is selected, that is, when there are many users in
each tracking area, service notification is sent to eNB 120 and UE
100 via output section 165 in ST 303 and ST 304, UE 100 is enabled
to receive the service no matter where UE 100 is located in the
tracking area and will not require any subsequent processing.
[0077] On the other hand, when SCT is selected, that is, when there
are only a few users in each tracking area, user number comparing
section 164 executes a procedure to check the presence of UEs and
counting in the entire tracking area in ST 303 and ST 304 to
deliver MBMS user data only to eNB 120 in which users exist.
[0078] The session start request in ST 303 includes an identifier
indicating MCT or SCT, and eNB 120 having received the session
start request thereby decides whether to perform service
notification or counting. Furthermore, likewise, the
notification/counting report in ST 304 also includes information as
to whether or not to perform counting and UE 100 decides whether or
not to respond to the counting.
[0079] Upon receiving information that counting is being performed
about the corresponding service from the service notification on
MBMS, UE 100 sets up an RRC connection in eNB 120 in ST 305 to
report to eNB 120 that UE 100 wants to receive the corresponding
MBMS. Here, using the RRC connection request message, UE 100
reports to eNB 120 that UE 100 wants to receive the corresponding
MBMS.
[0080] By recognizing the UE that transferred the RRC connection
request message, eNB 120 recognizes the presence of the user who
requests the specific MBMS within the cell and establishes an MBMS
radio bearer in ST 306 when at least one user exists.
[0081] In ST 307, eNB 120 sends out a multicast group joining
request to UPE 160 to construct an IP multicast tree in the IP
network between eNB 120 and UPE 160.
[0082] Each IP router and UPE 160, which have received the
multicast group joining request, store output interfaces where
users joining the service exist and thereby transfer the MEMS data
only to the necessary output interfaces.
[0083] The operation described so far completes a series of session
start procedures, and the MEMS data outputted from BM-SC 180 is
sent to UPE 160, the MBMS data is sent from UPE 160 only to eNB 120
in which MEMS users exist and finally sent to UE 100 joining the
multicast group.
[0084] Next, the maintenance of the delivery path of the MEMS data
set up by the above described session start will be explained. The
RRC connection between UE 100 and eNB 120 established in ST 305 of
the session start procedure is limited to the control plane that
transmits/receives only control signals.
[0085] Limiting the RRC connection to the control plane refers to a
state in which only the control plane is active, and refers to a
state in which only the entities related to radio link control
(RLC) on transmission/reception of RRC messages and media access
control (MAC) are included and neither reporting (CQI reporting) of
channel quality necessary for transmission/reception of the user
plane data of UE 100 nor monitoring or the like of the downlink
common control channel, is performed.
[0086] Therefore, UE 100 performs no transmission/reception of
signals other than reception of control signals related to MBMS and
service data unless UE 100 moves, and therefore UE 100 can suppress
battery consumption to a low level. Furthermore, the MBMS data is
intermittently received (DRX) at an interval appropriate for the
corresponding MBMS and it is thereby possible to further reduce
battery consumption.
[0087] By the way, the state in which only the control plane is
active is limited to between eNB 120 and UE 100 and no information
is supplied to MME 140 which performs position control over UE 100,
and therefore MME 140 continues position control over UE 100 on a
per tracking area basis.
[0088] eNB 120 can perform position control over UE 100, on a per
cell basis to maintain the RRC connection with UE 100. Therefore,
when UE 100 moves to another neighboring eNB, eNB 120 executes a
normal handover procedure and causes the RRC connection with UE 100
to be transferred to the target eNB. In this way, the target eNB
detects that the MBMS user has moved to come under control of the
eNB, outputs, if no such service has been provided, a multicast
group joining request, and provides a new service. Furthermore, if
there is no other UE 100 joining the multicast group, the source
eNB declares withdrawal from the multicast group to UPE 160.
[0089] Normally, UE 100 in the active state measures the received
quality of the neighboring cell and reports the measurement result
to eNB 120 on a regular basis or for each event.
[0090] Here, suppose UE 100 is located in the vicinity of the
boundary with the neighboring cell. eNB 120 having received the
neighboring cell received quality measurement result reported from
UE 100 detects that UE 100 is located in the vicinity of the
boundary with the neighboring cell.
[0091] Generally, in the case of SCT, received quality of a user
located in cell edges is known to deteriorate. Therefore, when a
user is located in cell edges, the mode is changed from SCT to MCT
and inter-cell diversity combination is performed.
[0092] FIG. 8 is a sequence diagram showing a procedure for mode
switching from SCT to MCT, and FIG. 9 is a block diagram showing
the configuration of eNB 120 according to Embodiment 1 of the
present invention. In FIG. 8, in ST 401, UE 100 measures received
quality in nearby cells under predetermined conditions and reports
the measurement result to s-eNB (i.e. source eNB).
[0093] In ST 402, the s-eNB having received the measurement result
detects that UE 100 is located in the boundary with a given
neighboring cell based on the measurement result, and in ST 403,
the s-eNB sends out a request for joining the multicast group to a
t-eNB (i.e. target eNB).
[0094] In ST 404, the t-eNB having received the multicast group
joining request sends out, when there is a resource for the t-eNB
to join the appropriate MBMS, the multicast group joining request
to UPE 160 via output section 125. The multicast group joining
request includes an identifier of the s-eNB and information
indicating switching to MCT.
[0095] In ST 405, UPE 160 having received the multicast group
joining request switches the transmission mode from SCT to MCT,
performs scheduling so that the s-eNB and t-eNB can output data in
synchronization with each other in ST 406, and reports the
scheduling result to the s-eNB and t-eNB respectively.
[0096] Parameter sections 122 of the s-eNB and t-eNB which have
received the scheduling result store the reported scheduling
information and reports the scheduling information to output
section 125. Output sections 125 of the s-eNB and t-eNB send out
MBMS data at timings defined respectively and UE 100 receives
combined signals from a plurality of cells, and the received
quality thereby improves.
[0097] Here, the configuration of above described eNB 120 will be
explained. In FIG. 9, input section 121 reports signals inputted
from UE 100, MME 140, UPE 160 and eNB 120 to parameter section 122,
cell edge detection section 123 and multicast processing section
124.
[0098] Parameter section 122 manages various parameters set through
signaling with UE 100, MME 140, UPE 160 and eNB 120 and MBMS data
is outputted from output section 125 as a transfer section
according to parameters specified by parameter section 122.
[0099] Cell edge detection section 123 of the s-eNB having received
the measurement result detects that UE 100 is located in the
boundary with a given neighboring cell and outputs an identifier of
the neighboring cell to multicast processing section 124.
[0100] When the own apparatus is the s-eNB, multicast processing
section 124 sends out a request for joining the multicast group to
the t-eNB that manages the neighboring cell through output section
125 based on the identifier of the neighboring cell outputted from
cell edge detection section 123.
[0101] Furthermore, when the own apparatus is the t-eNB, multicast
processing section 124 receives the group joining request and sends
out, when there are resources for joining the MBMS, the multicast
group joining request to UPE 160 through output section 125.
[0102] In this way, Embodiment 1 counts the number of UEs on which
tracking has been conducted for each tracking area including a
plurality of cells, selects MCT when the counted number of UEs is
equal to or greater than a predetermined threshold, or selects SCT
when the counted number of UEs is less than the predetermined
threshold, and can thereby appropriately switch between SCT and MCT
according to the number of UEs and can thereby reduce unnecessary
data delivery by MCT, reduce unnecessary counting by SCT and reduce
battery consumption.
[0103] In the present embodiment, UPE 160 compares the number of
users joining the service that exist in the MBMS area with a
predetermined threshold for each tracking area, but the present
invention may also be adapted so that a selected specific MME out
of the plurality of existing MMES compares the number of users
likewise.
[0104] The present embodiment detects that UE 100 is located in the
boundary with a given neighboring cell from the received quality
measurement result from UE 100, but the present invention may also
be adapted so that using a NACK prompting retransmission of lost
data sent out to eNB 120 by UE 100 when received quality
deteriorates, eNB 120 requests the neighboring cell to join the
multicast group upon receiving the NACK.
[0105] The present embodiment performs processing of comparing the
number of users shown in ST 302 of FIG. 7 using the number of UEs
on a per tracking area basis, but such processing may also be
performed per tracking areas.
Embodiment 2
[0106] Embodiment 2 of the present invention will explain a case
where SCT is selected, counting is performed and then UE 100
transitions to an idle state again. Since the network cannot
specify the movement of UE 100 in an idle state, recounting
(equivalent to counting) is performed on a regular basis to decide
whether to maintain or delete the MBMS radio bearer, on a per cell
basis.
[0107] When counting is performed, since response messages of UEs
requesting MBMS are generally concentrated on an upward channel
simultaneously, interference with and load on the uplink increase,
a probability factor (PF) is provided. Simultaneous responses are
avoided by only UEs that have produced random numbers which are
equal to or lower than the PF value transmitting an RRC response
message.
[0108] FIG. 10 is a flowchart showing a recounting procedure by eNB
130 according to Embodiment 2 of the present invention.
Furthermore, FIG. 11 is a block diagram showing a configuration of
eNB 130 according to Embodiment 2 of the present invention.
Hereinafter, the recounting procedure will be explained using these
figures.
[0109] eNB 130 reports an input signal from UE 100 to cumulative
count comparing section 131 through input section 121 as an
acquisition section.
[0110] In ST 501, parameter selection section 132 sets a first PF
value (parameter) upon starting a recounting procedure, and in ST
502, transmits the first PF value to UE 100 via output section 125
through a notification/counting report. UE 100 having received the
PF value compares the random number generated by UE 100 itself with
the PF value, transmits a response message when the random number
is equal to or below the PF value or waits until the next PF value
is received when the random number is greater than the PF
value.
[0111] In ST 503, input section 121 of eNB 130 receives the
response message from UE 100 and reports the received response
message to cumulative count comparing section 131.
[0112] In ST 504, cumulative count comparing section 131 as a
counting section counts the cumulative number of received response
messages and compares in ST 505 whether the cumulative count value
is equal to or greater than a predetermined threshold. The process
moves to ST 508 when the cumulative count value is equal to or
greater than the threshold (YES) or moves to ST 506 when the
cumulative count value is less than the threshold (NO).
[0113] In ST 506, cumulative count comparing section 131 decides
whether or not the number of tries of ST 502 to ST 505 has reached
a predetermined number of times (predetermined value). The process
moves to ST 509 when the number of tries has reached the
predetermined value (Yes) or moves to ST 507 when the number of
tries has not reached the predetermined value (No).
[0114] Since the number of tries has not reached the predetermined
value in ST 507, parameter selection section 132 selects a PF value
greater than the PF value used this time. Since a PF value greater
than the value this time is selected on the next try, more UEs 100
are expected to transmit a response message. After a number of
tries, if the decision result in ST 505 shows that the cumulative
count value is equal to or greater than the threshold, cumulative
count comparing section 131 commands recounting period selection
section 133 to select a recounting period and commands parameter
selection section 132 to select the first PF value.
[0115] In ST 508, eNB 130 knows that there are relatively many MEMS
users in the cell under control and since the probability that
certain users may continue to stay in the cell is high in the cell
where there are many users, recounting period selection section 133
sets a longer recounting period. This makes it possible to reduce
battery consumption of UE 100. Furthermore, for the next
recounting, parameter selection section 132 sets the first PF value
to a small value. This can avoid congestion of the uplink.
[0116] In ST 506, when the number of tries is decided to have
reached the predetermined value, in ST 509, cumulative count
comparing section 131 commands recounting period selection section
133 to select a recounting period or commands parameter selection
section 132 to select the first PF value next time. eNB 130 knows
that there are only a few MBMS users in the cell under control and
since all users may go out of the cell where there are only a few
users, recounting period selection section 133 sets a shorter
recounting period (default value). This makes it possible to
instantaneously detect a case where the number of users in the cell
is reduced to 0 and stop delivery of MBMS data to the cell to
thereby improve the utilization efficiency of radio resources on
the entire network. Furthermore, since the probability that the
uplink may be congested in the next recounting is low, parameter
selection section 132 sets the first PF value to a greater value.
This makes it possible to reduce the time required to complete
recounting.
[0117] In this way, Embodiment 2 reduces, when the number of users
in the cell is decided to be large according to the recounting
conducted in SCT, the battery consumption of each UE by extending
the recounting period and can reduce interference with and load on
the uplink due to simultaneous responses by reducing the first PF
value. On the other hand, when the number of users in the cell is
decided to be small, Embodiment 2 shortens the recounting period,
and can thereby instantaneously detect the case where the number of
users in the cell is reduced to 0 and improve the utilization
efficiency of radio resources on the entire network by stopping
delivery of MBMS data to the corresponding cell and shorten the
time required to complete recounting by increasing the first PF
value.
[0118] The present embodiment has explained two cases where the
number of users in the cell is large and small, but the present
invention is not limited to this and it is also possible to control
the recounting period and PF value in two or more cases of the
number of users in the cell.
Embodiment 3
[0119] Embodiment 3 of the present invention will explain a case
where SCT is selected, counting is performed and a transmission
mode is then selected again according to the distribution of eNBs
120 where MBMS users exist.
[0120] FIG. 12 is a block diagram showing the configuration of UPE
170 according to Embodiment 3 of the present invention. However,
parts in FIG. 12 common to those in FIG. 5 will be assigned the
same reference numerals as those in FIG. 5 and detailed
explanations thereof will be omitted.
[0121] In FIG. 12, input section 171 reports signals inputted from
BM-SC 180, MME 140 and eNB 120 to parameter section 162, user
number counting section 163 and eNB distribution check section 172.
Especially, input section 171 reports the number of MBMS users on a
per tracking area basis per service included in an MBMS
registration update to user number counting section 163.
Furthermore, input section 171 also reports an eNB identifier
included in a multicast group joining request and indicating eNB
120 in which MEMS users exist to eNB distribution check section
172.
[0122] eNB distribution check section 172 decides a distribution of
eNBs 120 where MBMS users exist, that is, a distribution with
respect to the entire tracking area based on eNB identifiers
outputted from input section 171. When the decision result shows
that the distribution of eNBs 120 where MBMS users exist satisfies
a predetermined condition, eNB distribution check section 172
selects MCT as the transmission mode in the tracking area or
selects SCT when the condition is not satisfied. An identifier
indicating the selected MCT or SCT is outputted to output section
173.
[0123] Output section 173 as a reporting section outputs the
service data outputted from parameter section 162, identifier
indicating MCT or SCT outputted from user number comparing section
164 and identifier indicating MCT or SCT outputted from eNB
distribution check section 172 to eNB 120.
[0124] Next, a session start procedure according to Embodiment 3 of
the present invention will be explained using FIG. 13. However,
parts in FIG. 13 common to those in FIG. 7 will be assigned the
same reference numerals as those in FIG. 7 and detailed
explanations thereof will be omitted.
[0125] In FIG. 13, in ST 601, eNB 120 sends out a multicast group
joining request to UPE 170 in order to construct an IP multicast
tree on an IP network between eNB 120 and UPE 170. In that case,
eNB 120 includes the identifier indicating itself in the multicast
group joining request as an eNB identifier.
[0126] Each IP router having received the multicast group joining
request stores output interfaces where there are users joining the
service.
[0127] In ST 602, UPE 170 having received the multicast group
joining request temporarily stores the eNB identifier included in
the multicast group joining request in eNB distribution check
section 172 and acquires multicast group joining request from all
eNBs 120 where MBMS users exist according to the count this time.
Here, eNB distribution check section 172 calculates the ratio of
the number of eNBs where MBMS users exist to the total number of
eNBs in the entire tracking area. When the ratio is equal to or
greater than a predetermined threshold, eNB distribution check
section 172 selects MCT as the transmission mode in the tracking
area or selects SCT when the ratio is less than the threshold.
[0128] When MCT is selected, the process moves to ST 603 and when
SCT is selected, UPE 170 stores the output interfaces where there
are users joining the service. When SCT is consecutively selected,
a series of session start procedure steps is completed, the MBMS
data outputted from BM-SC 180 is sent to UPE 170, sent from UPE 170
to only eNBs 120 where MEMS users exist and finally sent to UE 100
joining the multicast group.
[0129] UPE 170 has already reported to eNB 120 in ST 303 that SCT
was selected. Therefore, in ST 603, UPE 170 sends a transmission
mode change report indicating the switching from SCT to MCT to all
eNBs 120 in the tracking area.
[0130] The transmission mode change report in ST 603 includes
information about an identifier indicating MCT or SCT and
indicating whether or not to perform counting and eNB 120 having
received the transmission mode change report thereby decides
whether or not to change the transmission mode and also decides
whether or not to on a regular basis perform counting from this
reception onward.
[0131] This completes a series of session start procedure steps and
when there are only a few users per tracking area, yet a few MBMS
users are uniformly distributed with respect to the tracking area,
MCT is selected finally, and therefore UE 100 can receive the
service regardless of locations in the tracking area.
[0132] As explained in Embodiment 1, since the number of users per
tracking area is equal to or greater than a threshold, counting
need not be performed when MCT is selected, but if MCT is selected
because the number of users per tracking area is less than the
threshold and a few MBMS users are distributed uniformly with
respect to the tracking area, the ratio of the number of eNBs where
MBMS users exist to the total number of eNBs in the entire tracking
area may also change with the movement of UE 100, and therefore
counting is performed on a regular basis. That is, the processing
in ST 304 to ST 601 shown in FIG. 13 is performed on a regular
basis. Thus, UPE 170 performs the eNB distribution decision
processing in ST 608 every time counting is performed and selects
the transmission mode based on the result.
[0133] In this way, according to Embodiment 3, even when the number
of users per tracking area is less than a threshold, if a few MBMS
users are uniformly distributed with respect to the tracking area,
switching the transmission mode from SCT to MCT allows the amount
of signaling between eNBs and between each eNB and the core network
apparatus required for switching the transmission mode from SCT to
MCT to be reduced without reducing the utilization efficiency of
radio resources.
[0134] According to the present embodiment, eNB distribution check
section 172 switches the transmission mode based on the ratio of
the number of eNBs where MBMS users exist to the total number of
eNBs in the entire tracking area, but it is also possible to set up
an eNB identifier and information about the actual arrangement of
eNBs 120 beforehand, decide the actual distribution situation of
eNB 120 where MEMS users exist from the reported eNB identifier and
switch the transmission mode.
[0135] According to the present embodiment, eNB distribution check
section 172 switches the transmission mode from the distribution of
eNBs 120 where MBMS users exist when counting is performed, but it
is also possible to decide the distribution of eNBs 120 where MBMS
users exist based on the results of several counts and switch the
transmission mode.
Embodiment 4
[0136] Embodiment 4 of the present invention will explain the
operation of a cell in cell edges located in the boundary of a
tracking area where MCT is selected.
[0137] In the cell edge of a cell located in the boundary of a
tracking area where MCT is selected, when eNB 120 located in the
boundary of the neighboring tracking area (which corresponds to,
for example, eNB 3 and eNB 5 in FIG. 3) does not provide any
service, inter-cell diversity combination may not be successfully
realized and the service received quality may deteriorate.
Therefore, according to the present embodiment, eNB 120 located in
the boundary of a tracking area on a regular basis inquires of
N-eNBs 1 to n located in the boundary of the neighboring tracking
area about the MBMS delivery situation.
[0138] FIG. 14 is a sequence diagram showing inquiries of the MBMS
delivery situation between eNBs 120 located in the boundary between
different tracking areas. Multicast processing section 124 of eNB
120 located in the boundary of tracking areas is provided
beforehand with information that the own apparatus is located in
the boundary of tracking areas.
[0139] In ST 701 in FIG. 14, when providing MBMS in an MCT mode,
multicast processing section 124 of eNB 120 outputs service
inquiries to N-eNBs 1 to n located in the boundary between
neighboring tracking areas to inquire about the MBMS delivery
situation through output section 125. Service inquiries include
service identifiers indicating the corresponding MBMS.
[0140] In ST 702, input section 121 of N-eNB 1 to n, having
received the service inquiry, outputs a service identifier to
multicast processing section 124. Multicast processing section 124
decides the delivery situation of the service specified by the
service identifier, includes the result in a service response and
outputs the service response to eNB 120 which sent the service
inquiry through output section 125.
[0141] In ST 703, input section 121 of eNB 120, having received the
service responses, outputs the MBMS delivery situations of N-eNBs 1
to n included in the service responses to multicast processing
section 124. Multicast processing section 124 decides N-eNBs 1 to n
that need to join the corresponding MBMS from the MBMS delivery
situations of N-eNBs 1 to n. Here, "N-eNBs 1 to n that need to join
the corresponding MBMS" refer to N-eNBs 1 to n neighboring a cell
which does not provide the corresponding MBMS and in which there
are users requesting MBMS in the neighboring tracking area.
[0142] N-eNBs 1 to n that need to join the MBMS and eNB 120 which
has specified N-eNBs 1 to n perform the processing in and after ST
403 shown in FIG. 8 and thereby complete the joining in the
MEMS.
[0143] In this way, according to Embodiment 4, eNB 120 located in
the boundary of tracking areas on a regular basis inquiries N-eNBs
1 to n located in the boundary between neighboring tracking areas
about MEMS delivery situations, causes N-eNBs 1 to n not delivering
the MEMS in question to join the multicast group, and can thereby
reduce deterioration of service received quality of the cell in the
cell edge located in the boundary of tracking areas where MCT is
selected.
[0144] The present embodiment on a regular basis inquires of N-eNBs
1 to n located in the boundary between neighboring tracking areas
about the MBMS delivery situations and thereby decides the
necessity for N-eNBs 1 to n to join the MEMS, but it is also
possible to cause all MEMS users existing in the cell located in
the boundary of tracking areas where MCT is selected to transition
to an active state, perform cell edge detection as in the case of
Embodiment 2 and thereby cause N-eNBs 1 to n to join the MBMS.
Embodiment 5
[0145] Embodiment 5 of the present invention will explain timing UE
100 in an active state in a cell where SCT is selected sends out a
measurement report.
[0146] UE 100 in an active state in a cell where SCT is selected
measures received quality of a neighboring cell and reports the
measurement result to eNB 200 on a regular basis or event by event.
Hereinafter, a report on a received quality measurement result will
be referred to as a "measurement report." In this way, eNB 200
decides at which edge of the cell UE 100 is located and requests
the corresponding neighboring cell to join an MCT mode.
[0147] Here, the measurement report is sent on a regular basis or
event by event irrespective of the reception result of MBMS data,
that is, whether or not MBMS data has been received normally.
Therefore, UE 100 may send out unnecessary measurement reports and
consume the battery uselessly despite the fact that MBMS data has
been successfully received. On the contrary, despite the fact that
loss of MBMS data has been detected, time is required until the
timing a measurement report is sent out and a state of poor
received quality may continue.
[0148] Therefore, when UE 100 located in cell edges detects data
loss of MBMS, the present embodiment supposes that UE 100 sends out
a measurement report of the neighboring cell to eNB 200 triggered
by NACK transmission for requesting a retransmission of the lost
data.
[0149] FIG. 15 is a block diagram showing a configuration of UE 100
according to Embodiment 5 of the pre sent invention. In FIG. 15,
input section 101 outputs an MBMS data packet received from eNB 200
to received data decision section 102 and a reference signal
received from a neighboring cell to received power measurement
section 103 respectively.
[0150] Received data decision section 102 decides whether or not
the MBMS data packet outputted from input section 101 has been
correctly received. When the MEMS data packet has been correctly
received, received data decision section 102 transfers the received
packet to a higher layer. When the MBMS data packet has not been
correctly received, that is, loss of the received data packet is
detected, received data decision section 102 creates a NACK message
for requesting a retransmission of the lost data, sends out the
created NACK message to eNB 200 through output section 104 and
requests received power measurement section 103 to send out a
measurement report.
[0151] Received power measurement section 103 measures received
power for each neighboring cell using the reference signal
outputted from input section 101, receives the request from
received data decision section 102 and sends a measurement report
including an identifier of the neighboring cell and the measurement
result of received power to eNB 200 through output section 104.
[0152] FIG. 16 is a block diagram showing a configuration of eNB
200 according to Embodiment 5 of the present invention. However,
parts in FIG. 16 common to those in FIG. 9 will be assigned the
same reference numerals as those in FIG. 9 and detailed
explanations thereof will be omitted.
[0153] In FIG. 16, input section 201 stores an MBMS data packet
received from UPE 160 in buffer section 202. Furthermore, when a
NACK requesting a retransmission of lost MBMS data and measurement
report are received from UE 100, input section 201 outputs a
measurement report to cell edge detection section 203. When a
retransmission of a lost MBMS data packet is requested from
cumulative count comparing section 204, input section 201 transmits
the MBMS data packet stored in buffer section 202 to UE 100 again
through output section 125.
[0154] Cell edge detection section 203 detects the cell edge
bordering on a neighboring cell at which UE 100 which has sent out
the measurement report is located based on the measurement report
inputted from input section 201 and reports an identifier of the
detected neighboring cell to cumulative count comparing section
204.
[0155] Cumulative count comparing section 204 compares the number
of all users located in the cell edge with a predetermined
threshold for each neighboring cell reported from cell edge
detection section 203. When the comparison result shows that the
number of users is equal to or greater than a threshold, the
cumulative count comparing section 204 reports the identifier of
the corresponding neighboring cell to multicast processing section
124 or requests, when the number of users is less than the
threshold, input section 201 to retransmit an MBMS data packet
corresponding to the NACK out of the MBMS data packets stored in
buffer section 202.
[0156] The operations of cumulative count comparing section 204
after reporting the identifier of the neighboring cell to multicast
processing section 124 are the same as the operations in and after
ST 403 in FIG. 8 and therefore explanations thereof will be
omitted.
[0157] In this way, according to Embodiment 5, when UE 100 located
in cell edges detects loss of an MEMS data packet, UE 100 sends a
measurement report of the neighboring cell triggered by NACK
transmission requesting a retransmission of the lost data, thereby
sends out the measurement report to eNB 200 only in case of
necessity, and can thereby suppress the amount of battery
consumption of UE 100 to a low level. Furthermore, when there are
many users in the vicinity of the cell edge, it is possible to
efficiently improve the user's received service quality by
switching from SCT to MCT.
[0158] The present embodiment has explained on the assumption that
a NACK for requesting a retransmission of a lost MBMS data packet
and measurement report are transmitted separately, but a NACK and
measurement report may also be transmitted as one message.
Embodiment 6
[0159] Embodiment 6 of the present invention will explain a method
of efficiently counting the number of users existing in the
vicinity of cell edges bordering on a specific neighboring
cell.
[0160] Embodiment 5 compares the number of all users existing in
the vicinity of cell edges with a predetermined threshold for each
neighboring cell and requests the corresponding neighboring cell to
perform switching to MCT when the number of users is equal to or
greater than the threshold. However, there exist cell edges
corresponding in number to neighboring cells and since it takes
time for all users located in the vicinity of the cell edge to
uniformly send measurement reports and for the number of users
located in the vicinity of the cell edge bordering on a specific
neighboring cell to reach the threshold, inefficient
retransmissions may be repeated. Therefore, the present embodiment
limits transmissions of measurement reports to users located in the
vicinity of an edge with a specific neighboring cell.
[0161] Hereinafter, a method of sending a measurement report
according to the present embodiment will be explained using FIG. 15
and FIG. 16.
[0162] In eNB 200 shown in FIG. 16, parameter selection section 132
selects a cell identifier of a neighboring cell at predetermined
intervals and transmits the selected cell identifier to UE 100
through output section 125. The cell identifier is used to specify
a UE that sends out a measurement report amongst the UEs located in
the vicinity of cell edges and have detected loss of MBMS data
packets.
[0163] In UE 100 shown in FIG. 15, input section 101 reports the
cell identifier received from eNB 200 to received power measurement
section 103. Received data decision section 102 which has detected
the loss of the MBMS data packet requests received power
measurement section 103 to send out a measurement report.
[0164] Received power measurement section 103 decides whether or
not information about the neighboring cell corresponding to the
cell identifier reported from input section 101 is included in the
measurement report to be sent out. When information about the
neighboring cells is included, received power measurement section
103 sends out the measurement report to eNB 200 or stops, when
information about the neighboring cells is not included,
transmission of the measurement report. The subsequent operations
of eNB 200 of threshold decision and switching to MCT are the same
as those in Embodiment 5, and therefore detailed explanations
thereof will be omitted.
[0165] In this way, Embodiment 6 authorizes only UEs located in the
vicinity of cell edges bordering on a specific neighboring cell out
of UEs, which are located in the vicinity of the cell edge and have
detected loss of an MBMS data packet, to send a measurement report,
and can thereby efficiently count the number of users present in
cell edges bordering on the specific neighboring cell and promptly
perform switching from SCT to MCT for the corresponding neighboring
cell.
[0166] According to the present embodiment, parameter selection
section 132 selects a cell identifier of a neighboring cell at
predetermined intervals, but it is also possible to consecutively
select only an identifier of a cell neighboring a cell edge which
is predicted to have poor received quality.
[0167] The present embodiment authorizes only users located in the
vicinity of cell edges bordering on a specific neighboring cell out
of the users having detected loss of an MEMS data packet to send a
measurement report, but it is also possible to further combine the
PFs explained in Embodiment 2 and perform control so as to prevent
many measurement reports from being sent out simultaneously.
[0168] Also, although cases have been described with the above
embodiment as examples where the present invention is configured by
hardware, the present invention can also be realized by
software.
[0169] Each function block employed in the description of each of
the aforementioned embodiments may typically be implemented as an
LSI constituted by an integrated circuit. These may be individual
chips or partially or totally contained on a single chip. "LSI" is
adopted here but this may also be referred to as "IC," "system
LSI," "super LSI," or "ultra LSI" depending on differing extents of
integration.
[0170] Further, the method of circuit integration is not limited to
LSI's, and implementation using dedicated circuitry or general
purpose processors is also possible. After LSI manufacture,
utilization of a programmable FPGA (Field Programmable Gate Array)
or a reconfigurable processor where connections and settings of
circuit cells within an LSI can be reconfigured is also
possible.
[0171] Further, if integrated circuit technology comes out to
replace LSI's as a result of the advancement of semiconductor
technology or a derivative other technology, it is naturally also
possible to carry out function block integration using this
technology. Application of biotechnology is also possible.
[0172] The disclosures of Japanese Patent Application No.
2006-229811, filed on Aug. 25, 2006, Japanese Patent Application
No. 2006-274080, filed on Oct. 5, 2006 and Japanese Patent
Application No. 2006-310271, filed on Nov. 16, 2006, including the
specifications, drawings and abstracts, are incorporated herein by
reference in their entirety.
INDUSTRY APPLICABILITY
[0173] The core network apparatus, radio communication base station
apparatus and radio communication method according to the present
invention can improve the utilization efficiency of radio resources
of an entire network without increasing battery consumption of UEs
and are applicable to a transmission control system that delivers
MBMS.
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